The present invention relates to an anti-lock hydraulic brake system using a throttling valve which normally is open but which restricts flow to the brake line upon initiation of antilock control.
A like brake system is known from U.S. patent specification 3,829,166.
Herein an electromagnetically actuated valve operated by means of a control electronics is provided as a throttle valve. The valve is open in its initial position and releases the brake line. In the energized position, the cross-section of the brake line will be restricted so that the pressure fluid flow is throttled.
GB 21 01 245 A describes a brake system of the same type wherein the throttle valve is operated hydraulically. The pressure in the pressure fluid collecting means acts as switching pressure, the collecting means being designed as a low-pressure accumulator in this system.
It is the shortcoming of the brake system disclosed in the above U.S. patent that the electronic unit necessitates an expensive solenoid valve and additional drive modules.
The brake system according to the GB application inheres the disadvantage that the hydraulic valve is operated with delay only. Hence it is not safeguarded that rapid pressure reduction may take place.
The present invention has for its object to provide an anti-lock hydraulic brake system which is furnished with only a small number of electromagnetically actuated valves and which, in addition, safeguards a rapid pressure reduction.